CHANCE AND THE PREPARED MIND -Jack R. Holt

A WAKING DREAM large elm where the adults were calling. I To catch a bird, sprinkle salt on its tail to remember looking up into that tree and prevent it from flying away. -Anon. wondering if the bird would be able to make it I remember my grandfather as a weak, all the way to the first branch. I opened my sickly man. By the time I was old enough to hand, and the bird did not move. I then gave it a interact with him, he had suffered several heart small toss. It fluttered until it managed to land attacks and struggled with emphysema (The on a branch near the parents. family stories about him almost seemed to be about someone else). During that time we lived on the same lot as my grandparents; so I spent most of my time there. My grandfather didn't talk to me or carry on conversations. Usually, he put up with me or told me what to do. On a particular spring day, he had had enough of children's roughhousing and bickering. He singled me out as the instigator (likely that was true) and called me into his room, a place dominated by a large bed and TV. He didn't tell me to be quiet this time. Instead, he gave me a penny salt shaker and told me to go outside and catch a bird. He didn't explain why I should catch one, he just sent me on a mission, and I went. FIGURE 1. An old newspaper photograph of the He did not have to tell me how to catch the Washington Irving Monument with my bird, I had heard the story before. I just had to grandparents' house in the background. Tulsa pour salt on its tail…but how? I stood in front of Tribune, April 13, 1984. the large yellow stucco house that had been built on the site of Washington Irving's encampment My memory of that chance event is that I th during his tour of the prairie in the early 19 was surrounded by life. At that point, I was no Century. The City of Tulsa even erected a longer dreaming. Even now, everything seems monument to him in front of the house (see so vivid that I have trouble believing (except Figure 1). Motionless, I stared at that monument rationally) that the event occurred 40 years ago. trying to figure out how I was going to catch a I stood there on the flagstone path with the wind bird with salt. I don't know how much time in my face and the sounds of birds calling and elapsed. Suddenly, a flutter and thud broke my leaves rustling. The sights, sounds, odors all told waking dream. A baby Robin had flown out of a of life, that enigmatic process that defies strict nearby Juniper and landed at my feet. Quickly, I definition. fumbled with the salt shaker and dumped as much salt as I could all over the poor thing. THINGS THAT BURN Then, I scooped it up and returned triumphantly All the forms of matter which present themselves to the house with my prize. to our view, whether in the solid crust of the My grandfather had a good laugh, and the globe on which we live, in the air which forms bird amazed my siblings. I continued the the atmosphere by which we are surrounded, or triumphal procession into the kitchen where my in the bodies of animals and plants - all are mother and grandmother heard the story with capable of being divided into the two great disbelief. Then, they tried to talk me into giving groups of organic and inorganic matter. up my prize. Ultimately, they were successful, -James Johnston, 1857 but not without lots of persuasion. Living things like Robins and Elms have I went outside with my mother. The Robin particular properties that make them different squirmed in my hand especially when its parents from stones in the path and wind on my face. In began to call and show their displeasure with me. 1807 Jon Jacob Berzelius coined the terms I walked into the back yard and peered up into a "organic" and "inorganic" to recognize the distinctions between the products of life and all that calcium carbonate (CaCO3) had such a other material substances, respectively. Indeed, radical. The carbonate unit was made of one part these distinctions have been debated in science carbon and three parts oxygen with an overall since the Golden Age and continue in the debate charge of -1. about life in extreme environments on earth and Simple carbon compounds could be elsewhere. interpreted in the Dualistic Theory. For example Natural philosophers like Georg Ernst Stahl methane was made of one part carbon and four (1660-1734) solved the problem of the organic- parts hydrogen. Since hydrogen had a positive inorganic dichotomy by suggesting that the charge, carbon must have had a charge of -4. complexity of life (and its products) could be Carbon dioxide (one part carbon and two parts explained only by the existence of a vital force oxygen), however, required that carbon have a that provided the organizing principle and charge of +4 because each oxygen had to have a animating spark. (Recall that Galvani thought -2 charge. These problems seemed minor that he had discovered proof of that "spark".) compared to those posed by myriad other organic Although some inorganic substances such as compounds. Again, the vitalist principle hydrogen could burn, most did not. On the other provided the justification for the strange hand, almost all organic compounds could behavior of life's molecules. undergo combustion, and, when they did, they would release fixed air (or carbon dioxide) and AN ACCIDENTAL SCIENCE water among their byproducts. Lavoisier had It was like a dark forest with few or no pathways. concluded that the materials of life must contain -Woehler the elements carbon, hydrogen, and oxygen in The clear distinction and explanation that varying proportions. He determined that by separated organic from inorganic compounds heating materials such as wood or fat and changed dramatically following a simple set of collecting their constituent parts. This experiments by Friedrich Woehler (1800-1882). determination procedure remained the standard He had been an undistinguished student at the method for organic compounds through the University of Heidleberg from which he middle of the 19th Century. Nevertheless, the graduated with a degree in medicine. Later he accumulated results suggested that organic said that he spent much of his spare time compounds were quite bizarre when compared working on his own experiments in chemistry. with their inorganic counterparts. For example, With the blessing and advice of his mentor, iron combined with oxygen in a limited number Leopold Gmelin, Woehler went to Sweden to of ways in the production of compounds, while study in the laboratory of Berzelius with whom carbon combined with oxygen (and hydrogen) in he struck up a life-long friendship. He learned a bewildering number of ratios. the habits of precision and careful measurement A substance like iron oxide could be heated, that so characterized the work of the Swedish separated into its constituent elements, and chemist. After a year, Woehler returned to recombined to make iron oxide again. Sugar, a Germany and ended up on the faculty of a common organic compound, when heated would technical institute in Berlin. There, he began a smoke or char even if it did not burn. It could be very productive period during which his converted to its constituent elements (carbon- accomplishments included the isolation of hydrogen-oxygen) by burning, but those aluminum in the metallic state. elements could not be recombined outside of a Woehler's most lasting contribution came in living body to form sugar again. 1828 when he attempted to prepare a pure The behavior of inorganic substances like solution of ammonium cyanate (NH4CNO) from iron oxide could be explained. Berzelius had a mixture of silver cyanate (AgCNO) and established that compounds are constructed of ammonium chloride (NH4Cl). (Some sources say components (atoms) that have particular charges. that he mixed potassium cyanate and ammonium Thus, molecules like iron oxide are made of sulfate). He heated the preparation and allowed positively and negatively charged ions. For it to dry. As it did, long, white crystals began to example, iron can have a charge of +3 while grow. Woehler recognized the crystals (after oxygen has a charge of -2; so, hematite, an ore of some testing) as urea, a substance common in the iron oxide has an empirical formula of Fe2O3 urine of mammals (for example, an adult human (with a net charge of 0). Berzelius referred to typically excretes about 25g of urea per day). this electrical bonding as the Dualistic Theory. Urea had been isolated and characterized by H. Soon, he saw that clusters of atoms sometimes M. Rouelle in 1773. stay together as a charged unit or radical. Recall Woehler tested the "artificial urea" and Wilhelm Kastner and followed him to Ehrlangen pronounced, "it coincides perfectly with that of the next year. Liebig became caught up in the urea from urine." He had synthesized an organic political unrest of the university and spent three molecule from inorganic precursors. He had days in jail following a demonstration. That, found the chink in the armor of vitalism. He coupled with his disappointment in Kastner as a wrote to Berzelius: "I can no longer, so to speak, chemist caused him to petition the government hold my chemical water and must tell you that I (with the help of Kastner) for a grant to study in can make urea without needing a kidney, Paris. While there, with the support of whether of man or dog; the ammonium salt of Alexander von Humboldt, he studied under some cyanic acid is urea." of the greatest chemists of the day (Gay-Lussac and Thenard). Liebig continued his study of fulminates. He published his work on silver fulminate with Gay-Lussac in 1824. That same year Woehler analyzed silver cyanate in Berselius' laboratory. Both came up with the same empirical formulas for the compounds (AgCNO). The problem was that they had very different properties. In particular, silver fulminate was explosive and silver cyanate was not. The pugnacious Liebig assumed that Woehler was incompetent. However, when both men met in 1826 and did joint analyses, they recognized that two different compounds could have the same formula. Berzelius coined the term isomer (meaning equal parts) for such compounds. This encounter began a lasting collaboration and enduring friendship between the two men.

FIGURE 2. Friedrich Woehler. Image from: http://edie.eprost.sfu.ca/~rhogan/organic.html.

In 1836 Woehler obtained a teaching post at the University of Gottingen. Students flocked to study under him there where he is said to have trained around 8,000 before he died in 1882. Also, at Gottingen he continued his collaboration with his friend Justus von Liebig (1803-1873).

A FORTUNATE CHEMIST God has ordered all his creation by Weight and Measure. -sign above the door to Liebig's laboratory Liebig, like Woehler, was a tinkerer. His father was a dealer in paints and common chemicals, so he had a perfect laboratory in which to play. Later, he claimed that his experiments with fulminates (or other explosives) terminated several of his educational experiences (This seems to be apocryphal, FIGURE 3. Justus von Liebig. Image from: though). He did obtain a grant from the Hessian http://www.uni-giessen.de/~gi04/justus.html. government to attend the University of Bonn in 1820. There, he began to study under Karl Before Liebig's return to Germany, Kastner The candles used there during the reception gave managed to secure a teaching post at Erlangen off irritating fumes when burned. Dumas studied (and an honorary doctorate) for him. This was them and learned that they had been made of supported by von Humboldt in a letter to the wax bleached with chlorine. Thus, the burning Grand Duke who saw chemistry as a door to a candles gave off HCl gas (hydrochloric acid). brighter economic future. Thus, he moved the The puzzle was how the chlorine stayed in the chemistry instruction out of the medical school wax. Dumas realized that the element had and encouraged Liebig to move to Giessen in replaced some of the hydrogen in the carbon- 1824. There with state patronage Liebig began hydrogen chemistry of the wax itself. According to create a well-equipped research teaching to prevailing dogma (especially that of laboratory. His state support allowed for a large Berzelius), this was impossible. Chlorine had a laboratory budget and for qualified technicians negative charge while hydrogen had a positive who could create and maintain the equipment. charge. How could components with opposite Liebig argued that proper practical education in charges substitute for each other? At first the methods of chemistry required that the state Woehler and Liebig sided with Berzelius in the had to underwrite the education of its students. argument, but Dumas met with Liebig the next The state bought his argument and students year and demonstrated the substitution. After began to flock to Giessen not just from this, Berzelius' dualism view fell into disfavor Germany, but from the rest of Europe, and from regarding organic compounds. overseas. Dumas, Liebig, and other chemists through Liebig also succeeded because he had Europe began to see that organic molecules fell something of value to teach. His research into families. There were alcohols, organic program was focused and successful. During acids, esters, etc. Substitution reactions further this period, Liebig concentrated on the began to shed light on the nature of these classes determination and analysis of organic of compounds. However, the greatest mystery of compounds for which he developed rapid and organic chemistry remained unsolved. That is, accurate methods. what determined the particular properties of organic molecules anyway? Some isomers TABLE 1. Liebig's salary and laboratory budget melted at very different temperatures. Some (in florins) from 1824-1843 at Giessen. Adapted were soluble while their counterparts were not. from Brock (1992). How was this possible? After 1843 Liebig left the study of organic Year Salary Lab Budget chemistry (and Giessen) for physiology and 1824 300 100 biochemistry. Woehler returned to the 1825 500; 800 400 investigation of his beloved minerals. Berzelius 1833 880 619 tried to accommodate his Dualistic Theory to substitution but made no significant contribution 1835 1250 714 to organic chemistry after that. Although many 1837 1650 714 others continued the study of organic chemistry, 1840 3200 1500 it had reached a plateau with the realization that the properties of organic compounds had to be 1843 3200 1900 related to their most important element, carbon. A new view of carbon though required a new With Woehler, Liebig published a report vision, and the visionary was Friedrich August about a group of organic compounds that seemed Kekule (1829-1896). to have a common group, called the benzoyl group (C7H5O). This unit behaved like an A DREAMER inorganic radical in that it moved unchanged Let us learn to dream…then perhaps we shall from compound to compound (benzaldehyde, find the truth. -Friedrich Kekule (1890) benzoic acid, benzoyl chloride, etc). They Kekule went to the University of Giessen to published this as an example of an organic study architecture. However, he began to attend radical, a concept that Berzelius embraced, at Liebig's lectures and with some encouragement least for a time. decided to devote himself to the study of At the same time in Paris, Jean Baptiste chemistry. Liebig suggested that Kekule should Andre Dumas (1800-1884) had been asked to go to Paris and study under Dumas. Kekule solve a particular problem that occurred during a followed Liebig's advice and then went to reception given in the Tuileries by Charles X. England (1854-1855). While there claimed to have had a waking dream while riding atop a Kekule represented molecules as cryptic London bus. During his dream he saw atoms sausage-like horizontal structures (see Figure 5). dancing in the streets. A pair joined then another joined the pair. Lines joined lines at the ends while "all kept whirling in a giddy dance." The conductor woke him from his vision. He claimed years later that this was the start of the Structural Theory of organic chemistry.

ethyl alcohol acetic acid

FIGURE 5. Kekule's sausage formulas and Crouper-Brown graphic formulas for ethyl alcohol and acetic acid, respectively.

One of the first great triumphs of the Structural Theory came from Kekule himself when he determined the nature of a compound that had been isolated from coal tar. It was called benzene. Analysis of the molecule confirmed that it had 6 carbons and 6 hydrogens. However, it did not have the properties that one would expect for a 6-carbon molecule. In FIGURE 4. Friedrich August Kekule von particular, how could carbon have a valency of 4 Stradonitz. Image from: and still connect to only an equal number of http://www.rod.beavon.clara.net/kekule.htm hydrogens? Chemists assumed that it must be unstable and able to take on more hydrogens, but In 1858 Kekule adopted the current idea of the molecule resisted their attempts to saturate it. valence, that is atoms combine with a certain Kekule pondered the problem and came upon the number of others in making compounds. Kekule answer in a dream. He related the event of the assumed that carbon must have a valence of 4 discover years later: and that carbon atoms (unlike most other I was sitting writing on my textbook, but the elements) could link with themselves to make work did not progress; my thoughts were long, complex, and stable carbon molecules. elsewhere. I turned my chair to the fire and Thus, the structures (more than the component dozed. Again the atoms were gamboling elements) determined the properties of organic before my eyes. This time the smaller compounds. groups kept in the background. My mental Archibald Scott Crouper (1831-1892) eye rendered more acute by repeated visions independently came up with a similar Structural of the kind, could now distinguish larger Theory. In fact, his was more modern in its form structures of manifold conformation: long than that of Kekule. For example, Crouper rows sometimes more closely fitted together assumed that carbon could have a variable all twining and twisting in snake-like valence (how else to explain carbon monoxide motion. But look! What was that? One of and carbon dioxide as stable molecules). the snakes had seized hold of its own tail, Anyway, Kekule beat him into publication and and the form whirled mockingly before my into the history books. eyes. As if by a flash of lightning I awoke; A fellow Scotsman and colleague of and this time also I spent the rest of the Crouper, Alexander Crum Brown (1838-1922), night in working out the consequences of the took the stick or graphic formulas that Crouper hypothesis. had generated for organic molecules and began to popularize their use. The graphic formulas The hypothesis that he had stumbled on was saw popularity among those writing text books that the 6-carbon chain doubled back on itself in in Britain and Germany, so they were the forms a ring with alternating single and double bonds in which the new generations of students learned between the carbons. This kind of structure organic chemistry. That was fortunate because could make a stable 6-carbon and 6-hydrogen molecule. Kekule had deduced the structure Sources that I used to write the essay: based on the chemical description of the Brock, William H. 1992. The Norton History of properties of benzene and the valency of carbon. Chemistry. W. W. Norton & Co. New York. It was a remarkably elegant solution and quickly Cobb, Cathy & Harold Goldwhite. 1995. accepted by the scientific community. Creations of Fire. Plenum Press. New York. Fox, Marye Anne & James K. Whitesell. 1997. Organic Chemistry, 2nd ed. Jones and Bartlett Publishers. Boston. Harre, Rom. 1981. Great Scientific Experiments.

Phaedon Press, Ltd. Oxford. Holt, Jack R. & Patricia A. Nelson. 2001. Paths of Science, Explorations for Science Students and Educators. Kendall/Hunt Publishing Company. Dubuque, Iowa. Hudson, John. 1992. The History of Chemistry. Chapman & Hall. New York. Jaffe, Bernard. 1931. Crucibles, The Lives and Achievements of the Great Chemists. Jarrolds Publishers. London. Johnston, James F. W. 1857. Lectures on the Applications of Chemistry and Geology to FIGURE 6. Top, Kekule's sausage diagram of Agriculture. C. M. Saxton & Co. New York. benzene. Bottom, the modern structural formula Lavoisier, Antoine Laurent. 1789 Elements of for benzene. Chemistry. In: Hutchins, Robert Maynard, ed-in-chief. 1952. Great Books of the SERENDIPITY Western World. Vol 45. Encyclopedia In the field of observation, chance favors only Britannica, Inc. Chicago. the prepared mind. Louis Pasteur (1822-1895) Leicester, Henry M. 1956. The Historical Horace Walpole created the term serendipity Background of Chemistry. John Wiley & in 1754 to refer to accidental discoveries. Sons, Inc. New York. However, discoveries in science really are not Lundgren, Anders & Bernadette Bensaude- accidents. For example, organic chemistry Vincent, eds. 2000. Communicating developed by chance occurrences, dreams, and Chemistry; Textbooks and their Audiences, fortune, but the scientists all had minds prepared 1789-1939. Science History Publications. by study, opened by questions, and primed by Canton, MA. curiosity. Still, the accidental discoveries, like Roberts, Royston M. 1989. Serendipity, my capture of the Robin, did not happen for a Accidental Discoveries in Science. John purpose. The bird did not fall at my feet because Wiley & Sons, Inc. New York. I had a mission or a waking dream (or a penny Simmons, John. 1996. The Scientific 100, A salt shaker). I just took advantage of the Ranking of the Most Influential Scientists, situation as it presented itself. Past and Present. Citadel Press. New York. With the arrival of the Structural Theory, Trefil, James and Robert Hazen. 2000. The organic chemistry became modern in form, and, Sciences, An Integrated Approach. 2nd ed. following 1860, it, like Hermann Hesse's Prince John Wiley & Sons, Inc. New York. Dasa in Magister Ludi, "seemed to have been Weisberg, Robert. 1992. Creativity, Beyond the properly awakened and become ripe for setting Myth of Genius. W. H. Freeman. New York. out on the long journey." However, serendipity Internet Sources: continued to play an important role in its http://dbhs.wvusd.k12.ca.us/Chem- development as a science and the endless History/Wohler-article.html technological advances in areas like plastics and http://www.chemheritage.org/ other organic polymers, dyes, pharmaceuticals, http://www.rod.beavon.clara.net/kekule.htm food additives, etc. Ironically, the Structural http://www.woodrow.org/teachers/chemistry/inst Theory, which had become the death blow to the itutes/1992/Liebig.html Vitalist Principle in chemistry, gave science one http://www.uni-giessen.de/~gi04/justus.html of the most powerful tools to probe the wonderful chemical complexities of life itself. -March 2001 QUESTIONS TO THINK ABOUT

1. What were the distinctions between organic and inorganic? Why was combustion an inadequate way of distinguishing them?

2. How did the organic-inorganic dichotomy fit with the principle of vitalism?

3. How did Woehler demonstrate that those distinctions had to change?

4. What is the concept of isomer? Where did it come from?

5. Why was Justus von Leibig so successful?

6. What was the Dualistic Theory of Berzalius?

7. What were Kekule’s “waking dreams”? How did they influence chemistry?

8. What is the Structural Theory of Organic Chemistry? What theoretical problems did it solve?

9. Why was the structure of benzene such a problem? How did Kekule solve the problem of benzene?

10. Compare serendipity with Pasteur’s statement about the prepared mind. How do they come together to describe advances in science?